Lithuania had to go through a multitude of occupations in the 20th century. The occupational regimes both forced an abandonment of buildings that represented something "politically incorrect" to them and constructed buildings that were needed only under that particular ideology. Moreover, they also shuffled economy and demography. This led to Lithuania having a multitude of prominent derelict and semi-abandoned buildings, some of them having sad stories behind their abandonment.
1. Abandoned churches of Vilnius Old Town. The Soviet occupational atheist regime closed down most of Vilnius Catholic churches, destroying their interiors. Many were reopened but the most heavily damaged ones remain closed. After all, Vilnius Old Town has 1 church per every 700 inhabitants so the Roman Catholic Church prefers building new churches in the churchless Soviet-constructed boroughs rather than reopening further Old Town churches. Most of the abandoned churches are impressive 18th century Baroque ones. The following churches are now abandoned: Virgin Mary church (built 1768, Savičiaus st.), Lord Ascension church (built 1730, Subačiaus st.), Jesus Heart church (built 1765, Subačiaus st.), St. George church (built 1765, near Gedimino Avenue), St. Stephen church (built 1612, west of Train Station, downhill). Unfortunately, save for special occasions or personal arrangement with caretakers the abandoned churches could not be entered, but it is possible to explore an abandoned monastery near Šv. Ignoto street.
2. Kaunas fortress. This fortress actually encompasses the whole city. One of the largest and best-surviving class A fortress of the 19th century Russian Empire Kaunas withstood merely a few weeks of siege during World War 1, marking a major turning point in military history. Nobody ever built fortresses this big ever since and Kaunas fortress with its massive ring of forts, barracks towns, Orthodox churches and soldier cemeteries has been largely abandoned. While parts of the fortress have been reused (including museums in two of the forts, paintball in another one) most of it remains derelict and unlike many other such buildings in Lithuania may be freely explored.
3. Plokštinė nuclear missile launch site. The site was abandoned well before the Cold War ended (the Western spies found out about it) and much of the metal has been later stolen but a single fully equipped shaft (without missile of course) may be entered. A Cold War museum has been recently established inside.
4. Šilutė Lutheran cemetery, eerily overgrown by a forest and with no single gravestone intact, is like an unofficial monument to the Genocide of Lithuania Minor when the Soviets murdered 300 000 local Lutherans (Lithuanians and Germans) and expelled most others from this region in 1944-1949. The cemetery is older than that but the genocide left no relatives alive to care for the graves and the new settlers of Šilutė buried their dead elsewhere. Soviet era scavenging of elaborate metal fences contributed to the cemetery's sorry state but at least it was not demolished, unlike most Lithuanian religious minority cemeteries.
5. Kaunas Žaliakalnis Jewish cemetery is another similar unofficial memorial to a genocide, in this case, the Holocaust by Nazi Germany (1941-1944). The genocide victims aren't buried here but it was the mass murders and emigration of Lithuanian Jewry that left the cemetery uncared, graves all bent and drowning after heavy rains. Soviet policies against preserving historic cemeteries also contributed heavily.
6. Grūtas Park (near Druskininkai) is nicely landscaped and far from abandoned. The main draw here are, however, the abandoned Soviet propaganda sculptures and art, moved in from all the Lithuanian cities and towns in the 1990s after that regime collapsed (and liberated people toppled its monuments).
7. Spa Nemunas in Druskininkai. This massive abandoned complex of the 1980s dates to the Soviet idea of "controlled tourism" where every city would have just a single or a few large places of accommodation. Post-independence market economy preferred a larger amount of smaller hotels and thus Nemunas was abandoned (even though new modern spas have been built at the same time), marring the face of Druskininkai. Its multiple blocks cover an entire district ranging from the 10-floor main concrete building to numerous old wooden houses.
8. Ignalina Nuclear Power Plant in Visaginas once had the most powerful nuclear reactors in the world that provided Lithuania with 85% of its energy needs. The entire town of Visaginas has been constructed by Soviets to house its workers. The European Union requested Lithuania to close down the Soviet-built plant citing safety reasons. Its massive buildings now calmly stand at a lakeside, once bustling bus stops no longer used. The Nuclear question is still bitter in largely jobless and rapidly shrinking Visaginas where many believe the European Union requested the plant closure solely to protect its own market from cheap Lithuanian energy. Visaginas itself now also has some abandoned and never-completed residential buildings.
9. Palace of Sports and Concerts in Vilnius (Žirmūnai borough). Celebrated for its unique brutalist architecture the 5000-seat Soviet edifice became too small for Vilnius needs. Heritage status and its downtown location (on a place of a Soviet-demolished Jewish cemetery) ensured that replacements have been built elsewhere.
10. Palace of the Trade Unions in Vilnius New Town. Trade unions in the Soviet Union were controlled by the government (this being even more ridiculous since the government was also effectively the sole employer). However, being "workers institutions" in a (supposedly) workers society they were important for propaganda, so their lack of power has been compensated by pompousness of their edifices. That's how Lithuanian trade unions received this massive Stalinist palace on one of Vilnius tallest hills. Partly rented out and partly burnt out, the palace has been declining since independence. Every Saturday morning its vicinities host a flea market of antiques which may also interest fans of the "abandoned lives".